New research looking at the bone strength of European women living through the first 6,000 years of farming suggests they had quite the work ethic. So much so, their arms may have been stronger than today's elite rowers, with scientists claiming their findings point to a "hidden history" of physically demanding manual labor by women.

In looking to learn more about how ancient societies behaved, scientists have investigated the bone structure of women, but this was always done by comparing them directly with men. And because stress is more visible in male bones than female's, scientists at Cambridge University say that we may have been underestimating the kinds of strain women were putting themselves under.

"This is the first study to actually compare prehistoric female bones to those of living women," says Dr Alison Macintosh, lead author of the new study published today. "By interpreting women's bones in a female-specific context we can start to see how intensive, variable and laborious their behaviors were, hinting at a hidden history of women's work over thousands of years."

Macintosh and her team did this by using CT scans of leg and arm bones from women in the early Neolithic agricultural era (around 7,000 years ago), through to the farming communities of the Middle Ages (from 1,500 to around 500 years ago). These scans were then compared to those of an elite, record-breaking female rowing team from Cambridge University.

The team found that while the strength of the leg bones was similar to that of the elite rowers, the ancient arm bones were actually 11 to 16 percent stronger, and almost 30 percent stronger than a typical Cambridge student. Bronze Age women from around 4,000 years ago had arms bones that were 9 to 13 percent stronger than the rowers.

"We can't say specifically what behaviours were causing the bone loading we found," says Macintosh. "However, a major activity in early agriculture was converting grain into flour, and this was likely performed by women. For millennia, grain would have been ground by hand between two large stones called a saddle quern. In the few remaining societies that still use saddle querns, women grind grain for up to five hours a day. The repetitive arm action of grinding these stones together for hours may have loaded women's arm bones in a similar way to the laborious back-and-forth motion of rowing."

But Macintosh says it's unlikely that female labor was limited to this one task. Manual planting, tilling and harvesting were probably part of the workload, as were things like fetching food and water for livestock, processing milk and turning hides and wool into textiles.

"It can be easy to forget that bone is a living tissue, one that responds to the rigors we put our bodies through," Macintosh says. "Physical impact and muscle activity both put strain on bone, called loading. The bone reacts by changing in shape, curvature, thickness and density over time to accommodate repeated strain. By analyzing the bone characteristics of living people whose regular physical exertion is known, and comparing them to the characteristics of ancient bones, we can start to interpret the kinds of labor our ancestors were performing in prehistory."

The research was published in the journal Science Advances, and you can hear from Macintosh in the video below.